<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;

        }
        .box{
            background: #888;
            height:100%;
            margin-left: 50px;
            overflow: hidden;
        }
        .left{
            background: #73de80;
            border: 3px solid #f31264;
            width: 200px;
            height: 200px;
            opacity: 0.5;
            
        }
        .right{
            background: #ef5be2;
            opacity: 0.5;
            border: 3px solid #f31264;
            width: 400px;
            min-height: 100px;
        }
        /* .BFC{
            overflow: hidden;
        } */
        .little{
            background: #fff;
            width: 50px;
            height: 50px;
            margin-left: 10px;
            float: right;

        }

        
    </style>
</head>
<body>
    <div class="box BFC">
        <div class="left"></div>
        <div class="right BFC">
                      <div class="little"></div>
            <div class="little"></div>
            <div class="little"></div>
        </div>
    </div>
</body>
</html>